Question

An educational psychologist has developed a new method to improve reading and writing. However, before designing an experiment to test the new method, the psychologist needs to know if the assistants that will grade the essay are consistent. The psychologist has a random sample of students write an essay on the same topic. Every essay is then graded by every assistant on a 100 point scale. Below are the essay scores. What can the psychologist conclude with α = 0.05?

assistant 1	assistant 2	assistant 3	assistant 4
57 61 60 63 64 66 73 70	53 55 56 59 60 62 61 68	58 63 67 53 49 60 62 70	59 60 61 57 55 46 45 40

Compute the appropriate test statistic(s) to make a decision about H₀.
p-value =   

c) Using the SPSS results, compute the corresponding effect size(s) and indicate magnitude(s).
η² =

Answer 1

Solution

An educational psychologist has developed a new method to improve reading and writing. However, before designing an experiment to test the new method, the psychologist needs to know if the assistants that will grade the essay are consistent.

applying one way ANOVA:

Source of variation	SS	df	MS	F	p-value
Between Groups	532.8438	3	177.6146	4.3725	0.0120
With Groups	1137.3750	28	40.6205
Total	1670.2188	31

p value =0.0120 , reject Ho since p value <0.05

c) η2 =SS(BG)?SST =532.8438/1670.2188 =0.3190

effect size is large since η2 >0.25